Organizing Data and Information for Use in Decision Making

(MIS)

Views of Data

• The Physical View – Concerned with • The Logical View – Concerned with how data is represented so that it will be meaningful to users.

FILE in Access TABLE in Access

Bit: a single zero or one

• E (usually called simply Entity ) – It is a concept that relates to the items about which you wish to store information--these “items” can include conceptual ideas such as “philosophers’ thoughts,” people such as “student,” things such as “refrigerators” or places such as “city.” –

G

– EMPLOYEES Table

• Instance

– An of an

Entity Class

is called an of that class. Manhattan is an instance of the entity class city.

–

A More

– A record in Access

• Attribute

– C • Employee #, Last Name, First Name, Hire Date, Dept. Number – The columns in Access • A

PRIMARY KEY

is a field in a database file that – ID Number Social Security Number

Four main database models • Hierarchical • Network • Relational (the ) • Object-Oriented

Relational Database Model • Uses a series of two-dimensional called to store information relating to a • Tables = Relation: A specific entity class • Rows = or individual file folders.

• Columns = Attributes or • The relational database model is the widely used database model at the present time.

Spreadsheet Data Used to create a database

Steps to Create a Relational Database • Define entity classes and primary keys • Define relationships among entity classes • Define attributes (fields) for each relation • Use a data definition language to create the database.

Step One: Need a database that keeps track of the following information about your health club: The first name, last name, and id number for each of your members The address (street, city, state) where your members live The gender of each member and what class(es) they are taking The course name, number, and time that each of course meets The first name, last name, and id number for each of your employees.

The home phone number for each employee, as well as their salary amount and the date that they were hired.

Data Assumptions/Traits

• Member Number is unique. Each member will have only one Member Number. There is one Member for each Member Number.

• At this time, each member can enroll in only one course (at a time) that is offered by your health club .

Therefore, each member will have only one class number recorded at any time. (At some point in your assignment, you will make it possible for your members to take more than one course at a time) • Class Number is the unique identifier for each class that your health club offers. There is only one course for each class number.

• Employee Number is the unique identifier for each employee that works at your health club. There is only one employee for each employee number.

Data Assumptions/Traits

• A member can take only one course at a time.

• Only one instructor can teach a particular course.

• Only one section of a course is taught at any one time.

• A course may be taken by many different students.

• An instructor can teach more than one course at any one time.

• THEREFORE WE HAVE THE FOLLOWING ENTITY CLASSES: – MEMBERSHIP - primary key is Member Number – COURSES - primary key is Class Number – EMPLOYEES – primary key is Employee Number

Step 2 : Define relationships: between entity classes.

Using an Entity Relationship (E-R) Model Diagram, we can represent the entity classes and their MEMBERSHIP Key: Member Number 1:M COURSES COURSES 1:M Key: Class Number EMPLOYEES Key: Class Number Key: Employee Number STEP 3 : Define the attributes in each Entity which has been converted into a

Normalization • A technique used to make complex databases more efficient • Break one large – Eliminate all repeating groups in records – Eliminate – Assure that each field in the relation depends only on the primary key of that relation

Normalized Data: together by a in are found

A of this current example is that each member can . That is highly inefficient and it is not a good way to run your business.

Creating a allows you to store information in that table related to all of the different courses that your members are enrolling in.

•Class Number Enrollment table.

from the Membership table and placed in the •Neither Member Number nor Class Number is unique by itself in the Enrollment table. However, you can create a key that together, and that can be your unique identifier.

Step #4

: Use a Data Definition Language to create the database You need a database management system (DBMS) to do this

Microsoft is a software (database management system) that a that follows the principles found in the Model

What Is a Database Management System

An that provides all the necessary capabilities for b files, ex required for making decisions, and formatting the information into structured reports.

DIFFERENT FROM A DATABASE

DATABASE

a collection of information that you A database is actually composed of two parts: 1. The information itself / the files that are logically associated 2. The logical structure of the information which is called the data dictionary. The data dictionary contains the logical properties that describe information in a database.

DATABASE MANAGEMENT SYSTEM (DBMS)

the software you use to specify the logical organization for a database and access it.

A DBMS contains 5 software components:

Database Management System Engine

accepts logical requests from the various other DBMS subsystems, converts them to their physical equivalent, and actually accesses the database and data dictionary as they exist on a storage device.

You can work with the information

DATA DEFINITION SUBSYSTEM

helps you create and maintain the data dictionary and define the structure of the files in a database.

• A data dictionary serves the . as an • You use this subsystem to define the information logical when you first create a database.

• Once you’ve created a database, you use this subsystem to fields, fields, or field properties.

• •

What might be found in a data

F the

dictionary in Access?

and their , as well as I

are rules that help assure the quality of the information in a database. (Validation Rules in Access) – Setting a for a field – A birth date can be now or in the past: not in the future.

– A registration database at your school includes integrity constraints concerning for certain classes.

– Validation Text: seen in Access.

What might be found in a data dictionary in Access?

• Input Masks and Field Sizes • Formats, Default Values, and Captions • With

Referential Integrity

, you create a feature that will – When two different tables are linked/joined by a relationship where referential integrity is enforced, you cannot type data into a linked field if that same data does not already exist in the original table.

– You

DATA MANIPULATION SUBSYSTEM

helps you add, change, and delete information in a database and mine it for valuable information.

• This subsystem is most often the between you as a user and the information contained in a database.

• Tools in this subsystem include views, report generators, query-by-example tools, and structured query language.

DATA MANIPULATION TOOLS

• - allows you to see the content of a database file, make whatever changes you want, perform simple sorting, and search to find the location of specific information.

– Add records.

– Delete records – Sort records.

– Search for records.

DATA MANIPULATION TOOLS

•

REPORT GENERATOR

- helps you quickly define formats of reports and what information you want to see in a report. You can specify exactly what you want to see and where you want to see it.

– Report Wizard – Report Design Screen

DATA MANIPULATION TOOLS

•

QUERY-BY-EXAMPLE (QBE) TOOL

- helps you graphically design the answer to a question. You create this query • You specify that you want the database searched for, and the query tool will return records that match the conditions or criteria that you specified.

• Queries are used to useful

Query Design screen (above) and Query Result (below)

DATA MANIPULATION TOOLS

•

STRUCTURED QUERY LANGUAGE (SQL)

a standardized fourth-generation language found in most database environments. SQL is the same as QBE, except that you perform a query by creating a statement instead of pointing, clicking, dragging.

– SQL is a – Uses • • •

SELECT FROM WHERE

APPLICATION GENERATION SUBSYSTEM

contains facilities to help you develop transaction-intensive applications. This subsystem includes: • Tools for creating • Application buttons that are used to execute a certain task.

• Uses a programming language specific to the database management system that you are using.

DATA ADMINISTRATION

• B

SUBSYSTEM

helps you manage the overall database environment by providing facilities for: • Security management – W – W • Concurrency control ensures the validity of database updates.

• Change management allows you to assess the impact of proposed structural changes.

One of the goals of a database management system is to provide easy , while at the same time . If you have multiple files, each containing the same information, then you will most likely find redundant elements and erroneous data.

Relational Database Model • Uses a series of two-dimensional • Connects or relates data in different files through the use of a • Based on mathematical principles which allow for more logical manipulation of data.

• Most flexible type of organization.

THE CONCEPT OF KEYS •

A KEY

is a field or combination of fields used to identify records so they can be easily retrieved and processed.

• A

PRIMARY KEY

is a field in a database file that.

– I Social • You can create relationships between tables/files through /file.

Student and Department

Student Entity

.

.

Student Number Address Department ID

Department Entity

.

.

Department ID Address This way, if we wanted to know all the students that belong to a particular department, we could get the listing by joining the two entities on the Department ID value.

Relational Database Model

Driver’s license file/table Car owner file/table Moving violation citation file/table Parking violation citation file/table

State DMV Database Street address City State Zip Model year Car make Citation number Moving violation type Date cited Citation number Parking violation type Date cited 1XYZ234 Expiration date Street address City St.

Zip Fines paid/ not paid

Creating between database files.

– C /file.

– You might have to physically draw the connection between two tables/files. This is usually achieved by drawing a connecting line between two fields.

INFORMATION STORED SEPARATELY BUT CAN BE RELATED THROUGH KEY JOINS

Another example: which movies are provided by which distributors?

Recent Database Developments • The Data Warehouse and Data Mining • Object-Oriented Database Management Systems

Organizational Databases • Organizational databases are constantly changing as the organizational systems are constantly updating and changing the contents of the organizational database to reflect current business activities.

– Organizational databases support . Constantly being updated and changed.

– Not very useful for decision making involving the analysis of • Organizational databases rarely maintain historical data, just information related to current operations.

• A logical collection of information gathered from operational databases.

– Contains historical data that has been extracted from many different operational databases.

– Historical data is used for decision making.

• Operational databases support transaction processing (OLTP).

• Data warehouses support (OLAP) because historical data is analyzed in order to make • D are the software tools used to query information in data warehouse.

– Use advanced statistical techniques to search for patterns and anomalies in the data.

– Attempts to find answers to questions the user did not even think to ask.

• A relational database stores information in a series of .

• Data warehouses are Each dimension is an of information.

, containing

D perform analysis in data warehouses

•

C

– common term for the representation of multi dimensional information ( )

• • • • • • Applications of Data Mining

M

: identifying common characteristics of customers who buy the same products from your company.

Customer Churn

: predicting which customers are likely to leave your company and go to a competitor.

F

: identifying which transactions are most likely to be fraudulent.

Direct Marketing

: identifying the best prospects in order to obtain the highest response rate.

Market

: trying to understand which products are commonly purchased together.

T

: trying to reveal differences between one period and another period.

• Info in an Excel spreadsheet and a relational database (Access) appears in the form of a two dimensional table of rows and columns.

• By adding a add and columns and layers).

, you can : 3-D (rows – Creating a 3-dimensional Pivot Table in Excel is a means of conceptually building a data warehouse. Page fields represent the depth layer • Pivot Tables can help you see relationships in the data

• The following are summary slides that I don’t plan on covering in class, but I am making available for you to review, if you wish.

• The Interpreting SQL slides will be seen at a later date (after everyone has made queries in lab)

TO SUMMARIZE

• How we view information: – The physical view of information deals with how information is physically arranged, stored, and accessed on some type of secondary storage device.

– The logical view of information focuses on how you need to arrange and access information to meet your particular business needs.

• A database is a collection of information that you organize and access according to the logical structure of that information.

• The data dictionary contains the logical structure of information in a database.

Database Models • Relational Database Model – All the data is arranged in a series of related tables. Student, Class, Instructor – Tables are linked together by common fields.

• Object-Oriented Database Model – Allows you to store the data and the procedures used to manipulate that data together.

– Can be used to store text, sound, video, and images.

– Stores data, computes GPA, and creates a transcript.

Normalization • Used to create tables in a relational database.

• Break one large table into several smaller tables – Eliminate redundant data (duplicate copies) – With redundancy removed, you only need to make a change once and all linkages are automatically updated.

Proper Database Design • Field: Name: Brian Kovar • Field: Address: – 123 North Main, Manhattan, KS 66502 •Field: Last Name: Kovar •Field: First Name: Brian •Field: Address: 123 North Main •Field: City: Manhattan •Field: State: KS •Field: Zip Code: 66502

Interpreting SQL Code

•

SQL

(The language used to query a database) S is used to specify the you want to include.

• F is used to specify the the selected fields are coming from.

• • • W is used to used to narrow down the data prior to being displayed.

O is used to specify how the records (in ascending or descending order), as well as the sort order.

I the specifies that two or more tables are and it also specifies the field that forms between the tables.

• • • • S the following fields from the Employees table: Last Name, Title and Salary. The used to narrow down the records is where the title is “Sales Representative.” The results should be in descending order (high to low number order) based on salary. All of the fields in the query come from the Employees table.

SELECT Max(Employees.Salary) AS MaxOfSalary, Min(Employees.Salary) AS MinOfSalary, Avg(Employees.Salary) AS AvgOfSalary, StDev(Employees.Salary) AS StDevOfSalary FROM Employees; Select the Salary field from the Employees table (4 times). Find the maximum salary, the minimum salary, the average of salaries and the standard deviation of salaries.

• Select the following fields from the Customers table: Company Name, City and Country. • The criteria used to narrow down the records is where the country begins with U (it does not matter what comes after the U as long as the first letter of the country is a U). • All of the fields in the query come from the Customers table.

All of the fields in the query come from either the Customers table or the Orders table.

The Customers and Orders tables are joined together by the common field of Customer ID (Inner Join signifies this).

Select the following fields from the Customers table: Customer ID and Company Name. Select the following fields from the Orders table: Order Date and Shipped Date.

The criteria used to narrow down the records is that the company name should match “B’s Beverages”.

• • O is used to specify how the records should be sorted (in ascending or descending order), as well as the sort order.

F uses the city field and the records are sorted in alphabetical order by city (order by defaults to ascending order) • If there happen to be multiple entries from the same city, a (descending order by last name)